Artificially colored granules and method of producing same



- I U TED STATES f Patented Sept. 24, 1940 PATENT OFFICE an'rmcmtr COLORED GRANULES sun mnrnon or rnonucnvo sam: Marion n. Veazey, Rutherford, N. 1., assig'nor to The Patent and LicensingCorporation, New York, N. Y., a-corporation of Massachusetts No Drawing.

Application March 7, 1935, i a: Serial Nosiifliiii 9 Claims. (01. 91-40) This invention concerns improvements in the production, of artificially colored granules and more particularly artificially colored granules to be used as a surfacing for materials subject to "exposure to the weather, as for example mineral surfaced roofing, siding or the like;

- Processes have heretofore been in use 'for'the artificial coloring of granules to be used as a surfacing for asphalt coated roofing in order to 10 obtain colorings which are not available in the natural sources of supply of the mineral base, as for example crushed slate, etc. Chief among the processes that have heretofore been proposed is one wherein the pigment or is coloring agent is afllxed to the surfaces of the granules by means of soluble silicate and p rticularly sodium silicate. .It becomes necessary therefore in these processes to insolubilize the silicate in order that the coating of artificial'colorlng may be made permanently weather resisting, or

tight as it is sometimes referred to. It therefore heretofore been proposed to heat the coated granules in retorting apparatus at temperatures, sumciently high to eiifect insolubfliza- 252 tion of the coating, the temperatures required for this purpose varying from 900 to 1500 F. de-

pending upon the conditions of the operation. It

haslikewise been proposed .to eflfect insolubiliza- .tion of the silicate coating bychemical action so-punder conditions which would avoid the necessity of retortingthe granules atsuch high tempera! tures, thus reducing the cost of'the equipment necessary andalso the fuel cost and at thesame time making it possible to employ pigments which are harmfullyaflectedwhen-the'hish retorting I temperatures are employed. This chemical method of insolubilization has been utilized by taking advantage of certain classes or types of base granules which are, .or which carry con-;

40 stituents that are, reactive toward soluble silicate. permitting the insolubilimtion to take placev at temperatures of from 250 to'650F. In other instances this method of insolubilization, where the base. granule is not itself reactive, toward soluble silicate, has been carried out by incorporating in the mixture'of the sodium silicate,

and h pigment with'which the granules are coated, a re-agent, such as certain compounds which under, the conditionsof operation will react with the soluble silicate and permit insolubilization to take place at comparatively lower;

Ithasbeenhowevenforaconsiderable period of time that while the coloring of granules cacoatedbythaepwhereineodlumfl icatc' fests itself inthe form of a white or'opaque and 10 more or'less bulky deposit on the granules, when the finished granules made by the processesabove describedare moistened with water and the water subsequently evaporated.

In my earlier co-pending application Ser. No; 15

137,774, filed July 31, 1934, I have described in 7 detail this blooming effect, and theapparent mechanism by which it occurs, .1 have therein described and-claimed certain methods whereby to eliminate blooming tendency in granules g0 artificialLvcolored by the processes wherein use is made of soluble silicate such as sodium silicate as the binding or fixing agent. As stated in my said-cor-pending application, it appears that this blooming effect is due to the presenceof sodium 25 carbonate in the film of the coating material.

' This sodium carbonate apparently results chiefly I from the reaction between the hydroxide present in the sodium silicate used in the coloring process and carbon dioxide present in the flue gases with 30 which the granules are heated in order to bring the colored coating to the insolubilized, state.

' Some of this "blooming effect is apparently due also to the presence in the film of certain amounts pf sodium hydroxide (free alkalicontained in the 5 sodium silicate) which, when leached out on contact with moisture, slowlyreacts with the carbon dioxide of the air to form sodium carbonate.

In nay said earlier application I disclosed methods for overcoming this blooming effect, accord- 4 ing to which the absorption of carbon dioxide by the alkali contained in the film of silicate during the passage of the coated granules through the a retort or kiln,-'may be prevented. Also, I disclosed therein certain separate steps of treating 45 the granules, after they havebeen'retorted, with material which would remove from the film of the finished granules such sodium carbonate and sodium hydroxide as might be present therein and give riseto the blooming eflect; 50 My presentinvention has for its object the production'of artificially colored granules,- utlliz- 1 ingsodimnsilicateastheflxingorbind nz ent' for the pigment, in which the normal tendency of suchgramiles to exhibit theblooming? eflect more expeditious than those set forth in my said co-pending application, with the production of granules which will not only be non-blooming but which also have a tight and weather resisting coloring film.

My present invention and the means by which the objects thereof are accomplished are based upon the reaction of sodium silicate with materials which produce reaction products all of which are substantially insoluble in water. The reacting materials which I employ in accordance with my present invention for reaction with the soluble silicate also reacts with the alkali which may be present in the sodium silicate, so that the resulting granules are neutral. This neutralization of the alkali therefore avoids the possibility of absorption of carbon dioxide by the alkali to produce sodium carbonate, which is the material that really causes the blooming, as explained in my aforesaid co-pending application. The silicate is insolubilized with the production of reaction products that are substantially insoluble in water. At the same time, the insolubilization of the silicate may be eifected at low temperatures varying from room temperature to 650 F., thus retaining all of the above stated advantages of products with the soluble silicate, all of which are substantially water-insoluble.

The importance of utilizingreagents to effect insolubilization with the production of reaction products that are insoluble in water or substantially so resides in the fact that many water soluble or partly water soluble salts may themselves be oi bloom forming character, as distinguished from sodium carbonate which, as explained in my aforesaid application, gives rise to a bloom by becoming converted under conditions that the granules meet in service, into a hydrated salt that forms a bloom.

I have found that certain types of fiuosilicates which are normally only slightly soluble in water, such as barium fiuosilicate, react with sodium silicate in such a way that the reaction products are practically insoluble in water. Commercial barium fiuosilicate is acid, imparting a pH of somewhere between 3.0 and 5.0 to water in which it is immersed and its solubility varies from 0.02 to 0.09 gram per cc. of water depending upon the temperature. The reaction between barium fiuosilicate and sodium silicate takes place at normal temperature in a relatively short period of time and the rate of reaction can be controlled to a certain-extent by the amount of water present.

The reaction may be represented by the following equation:

Na2SiO3+BaSiF6 BaSiOs-i-NazSiFc In the above equation the barium silicate which is one of the products of the reaction is insoluble in water,. while the sodium fiuosilicate in service is eliminated by methods simpler and which is the other productof the reaction, is soluble in water to only a slight extent, namely 0.65 gram per 100 cc. at 17% C.

In actual practice of the process utilizing barium fiuosilicate as the reagent in accordance with the above equation, -it is found that much less than metathetical proportions of the barium fiuosilicate are required because the greater portion of the sodium silicate is insolubilized by the dehydrating action under the conditions of operation and it is necessary therefore that the barium fiuosilicate shall react only with the soluble portion of the sodium silicate, namely that portion which is not insolubilized in drying.

In the practice of my invention the granules may first be mixed with the required amount of sodium silicate and the desired pigments or with a suspension of the pigment in the silicate. After being mixed, the barium fiuosilicate is added in the form of a finely divided powder or as a paste with the least possible amount of water, the mixing being continued for a little time longer. The order of mixing however is not critical and in certain instances it may be preferable to mix the dry granules with the pigments and the barium fiuosilicate followed by adding the required amount of sodium silicate and continuing the mixing for a few more minutes. In either event, however, an excess of water should be avoided as such excess appears to impair the color of the finished granules in certain instances and also requires larger quantities of the barium fiuosilicate. This reagent, being a rather expensive one, should of course be employed in the minimum quantities necessary to produce the desired results. The larger quantities necessary to produce these i;- sults when an excess of water is present during the mixing is apparently due to the fact that with such excess of water a greater amount of the barium fiuosilicate in solution is consumed in reacting with the soluble portion of the sodium silicate. This, as above stated, is not necessary where heat is also employed because the action of the heat insolubilizes the greater part of the sodium silicate and it is necessary therefore only to use such an amount of the barium fiuosilicate as will react with the remainder of the sodium silicate and with any sodium hydroxide and sodium carbonate that may be present. The use of the barium fiuosilicate in the process herein described.

accordingly may be more or less interchangeable in respect to the quantities employed, with the degree of heat employed in treating the coated granules. This will more fully appear from the specific examples given hereinbelow.

By this treatment I have found it is possible to obtain artificially colored granules utilizing soing of the coating and thus avoid the retorting' tion I have been able to produce an artificially colored granuleutilizing Pennsylvania glass sand as the base granule. 400 parts by weight of these granules were mixed with four parts of lead chromate for the production of a yellow granule and with parts of barium fiuosilicate and 24 parts of sodium silicate, 4 parts of water being included in the mix to provide proper workability.

The sodium silicate employed was a commercial grade known as N brand, in which theweight ratio of Nazi) to S10: is 1:325 and containing 62% of water. The granules as thus coated after being air dried for 48 hours at room temperature showed, when subjected to the usual wash tests,

a satisfactory tightness, there being only a slight or negligible loss and the film of the pigmented reaction product being firmly adherent to the base granules. Specifically, five successive washings of a 25 gram sample of the dried granules with hot water showed a loss of only 0.003 gram. Also, extraction of the granules with cold water showed the presence of only very low amounts of hydroxide or carbonate, the values obtained by titration of the water extract with phenolpthalein indicating quite conclusively that the amount of bloom from these granules would be entirely negligible. Also, separate blooming tests as mixed'with 4 parts by weight of chromic oxide (CrzOa) for the production of a green granule, and with 24 parts of sodium silicate, 4 parts of water, and with 2% parts of barium fiuosilicate. The thus coated granules were dried in a kiln at temperatures between 550 and- 600 F. and the finished granules likewise showed satisfactory tightness and also no indicationof any tendency to bloom. Specifically, the washing of 25 gram samples of the finished granules five successive:

' times with hot water showed a loss of only 0.010

gram insoluble matter. Cold extraction tests. i. e., when 50 grams of the finished granules were extracted with col? water showed complete neutrality upon titration with phenolphthalein, thus indicating that there was neither sodium carbonate nor sodium hydroxide present on the.

granules and that therefore the finished granules would exhibit no tendency to bloom. This was confirmed by separate blooming tests.

, Comparing the foregoing specific example with the one first above given it will be noted that in the one case the requisitetightness of the film and its freedom from blooming is obtained by air drying the coated granules utilizing 5% parts by weight of barium fiuosilicate with 24 parts of sodium silicate to treat 400 parts of granulu: whereas in the other case,,utilizing heat oi the order of 550 to 600F. substantially the same results are obtained with only 2% parts by weight of barium fiuosilicate for treating the same amount of granules with the same amount of sodium silicate.

while I have hereinabove explained what I believe to be the theory underlying the results obtained by my invention and have depicted the samg-pymhemical equations, it is to be under-f stood I do'not wishto be confined to such or reactions which occur in carrying out the invention may be much more complex than that stated. The fact remains however that the results herein stated are obtainable by carrying out the invention in the manner described.

theory as it is quite possible that the reaction In lieu of barium fiuosilicate as the reagentin the process according to the present invention there may be employed the commercial form of sodium fiuosilicate. This commercial form of sodium fiuosilicate is slightly soluble and has an acid reaction in solution.

I claim:

1. The method of artificially coloring granules which comprises coating the granules with a mixture of pigment, soluble silicate, and a slightly soluble fiuosllicate adapted to react with the silicate with neutralization of the alkali, and then drying the granules, the proportions of said fluosilicate. in relation to the soluble silicate being sufilcient to produce granules substantially devoid of free alkali and of water-soluble salts.

2. The method of artificially coloring granules which comprises coating the granules with a mixture of pigment, sodium silicate, and barium fiuosilicate and drying the granules at the temperatures below 650 F.

3. The method of artificially coloring granules which comprises coating the granules with a mix- I ture of pigment, sodium silicate, and barium fiuosilicate, and then drying the granules at temperatures below 650 F., the proportion of barium fiuosilicate in relation to the sodium silicate being such as to produce granules which are of neutral reaction and free of salts oi'appreciable 33 water-solubility. i

.4. The method of coloring granular material comprising spreading coloring agent, barium fiuosilicate and an aqueous dispersion or alkalimetal silicate over the surfaces of the granular material and drying the coated granules.

5. The method of coloring granular material comprising spreading coloring agent, sodium -fiuosilicate and an agueous' dispersion of alkalimetal silicate over the surfaces of the granular material and drying the coated granules. 8. Roofing granules which consist of granul mineral nuclei individually carrying upon substantially all. their surfaces a coating of the low temperature reaction products of barium fiuosilicate, alkali-metal silicate in an aqueous dispersion, and a coloring agent.

7-. Roofing sheets surfaced with the article of claim 6. g 8. As a new article of manufacture, roofing. granules of the class described having on the exterior thereof a substantially non-blooming, insoluble coating, said coating consisting substantially of the reaction product of sodium fiuosilicate and sodium silicate. and beingsubstantially free from water-soluble salts of sodium.

9. As a new article of manufacture, roofing granules of the class described having on the exterior thereof a substantially non-blooming, in-

soluble coating, said coating consistins'substantially of pigment-and the reaction product of so-' dium fiuosilicate and sodium silicate, and being zgistantially free from water-soluble salts of more a. vnaznr. 1o 

